JP2524844B2 - Aluminum alloy plate having a beige color tone after anodizing treatment and method for producing the same - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an aluminum alloy material used for anodizing treatment, in particular, a building material such as a building curtain wall or an interior material, or an instrument, a container, an electrical measuring instrument. The present invention relates to a method for manufacturing an aluminum alloy plate material used for a case, a decorative article, and the like.

2. Description of the Related Art In general, aluminum alloys used for building materials such as curtain walls and interior materials, or for appliances, containers, housings of electrical measuring instruments, etc. are often anodized from the viewpoint of corrosion resistance. As anodized aluminum alloys for these applications, there are many light gray to silver type alloys, and such alloys are generally JIS 1050.
Alloy, 1100 alloy, 5005 alloy, etc. are often used,
Al-1 to 4% Si alloy is generally used as the gray type. Further, as the anodizing treatment, a sulfuric acid electrolytic bath is often used from the viewpoint of economy and corrosion resistance.

By the way, in the above-mentioned applications, it may be required that the surface after the anodizing treatment has various color tones for the sake of aesthetic appearance. As a method for giving a desired color tone to the anodized plate, there are coating, dyeing, secondary electrolytic coloring, alloy coloring, coloring by an anodizing solution, etc., but from the viewpoint of economical and corrosion resistance, Oxidizing treatment,
In particular, it is desired to develop the color by the anodizing treatment in a sulfuric acid bath.

Problems to be Solved by the Invention Among various color tones, a beige color tone with less metallic luster gives a moist and calm texture, and since it gives psychological warmth and a sense of security, it is also used in building materials and the like. Beige tones with less metallic luster are often required. However, conventionally, it has been extremely difficult to obtain an anodized plate having a beige color tone with little metallic luster by the anodizing treatment as it is, particularly as it is in the sulfuric acid bath.

This invention was made against the background of the above circumstances.
An aluminum alloy plate that can obtain a beige color tone with little metallic luster with anodizing treatment using a sulfuric acid bath, a method for manufacturing the aluminum alloy plate, and further anodizing using the aluminum alloy plate. It is an object of the present invention to provide a method for achieving a beige color tone having less metallic luster by treatment.

Means for Solving the Problems In order to achieve the above-mentioned object, as a result of repeated experiments and studies by the present inventors, the content of alloying elements, particularly the Fe content and the Mn content, are adjusted to appropriate amounts. As a result, they have found that a beige color with less metallic luster can be obtained as a color tone after anodizing treatment in a sulfuric acid bath by appropriately determining the type and amount of the intermetallic compound, and the present invention has been accomplished.

Specifically, the invention of claim 1 provides an aluminum alloy plate capable of obtaining a beige color tone with less metallic luster after anodizing treatment, and Fe 0.8 to 2.0 wt.
%, Mn 0.05 to 0.4 wt%, Si is regulated to 0.2 wt% or less, the balance is substantially made of Al, and FeAl ₃ phase and FeMnAl with respect to the total amount of intermetallic compounds (weight). _The ratio of the total amount of the _three phases is 90% or more, and the total amount of intermetallic compounds is in the range of 2.5 to 7.0 wt%.

The invention according to claim 2 provides a method for producing the aluminum alloy plate, wherein Fe 0.8 to 2.0 wt%,
An aluminum alloy containing Mn 0.05 to 0.4 wt% and Si regulated to 0.2 wt% or less, and the balance substantially consisting of Al, and after DC casting of the alloy, 580 to 580 to the ingot 630
Heat treatment is performed for 0.5 to 24 hours at a temperature within the range of ℃, and then rolled to obtain the final plate thickness, whereby the total amount of FeAl ₃ phase and FeMnAl ₃ phase accounts for the total amount of intermetallic compounds (weight). The proportion is 90% or more, and the amount of all intermetallic compounds is
The feature is to obtain a rolled plate in the range of 2.5 to 7.0 wt%.

Furthermore, the invention of claim 3 provides a method for producing an aluminum alloy having a beige color with little metallic luster by actually performing anodizing treatment, and Fe0.8 to 2.0
An aluminum alloy containing wt% and Mn of 0.05 to 0.4 wt%, Si regulated to 0.2 wt% or less, and the balance substantially consisting of Al is used as a raw material. Against 58
Heat treatment is performed for 0.5 to 24 hours at a temperature in the range of 0 to 630 ℃, and then rolled to the final plate thickness, which gives the total of FeAl ₃ phase and FeMnAl ₃ phase to the total amount of intermetallic compounds (weight). To obtain a rolled plate having a ratio of 90% or more and a total intermetallic compound amount in the range of 2.5 to 7.0 wt%, and thereafter, the H ₂ SO ₄ concentration of the rolled plate is 10 to 25 vol%. Using sulfuric acid electrolysis bath, bath temperature 10 ~ 30 ℃, current density 1.5A / dm ² or more, 2.
It is characterized in that an anodic oxidation treatment is performed at less than 5 A / dm ² to form an anodic oxide film having a film thickness of 10 to 30 μm.

Action First, the reasons for limiting the composition of the aluminum alloy will be described.

Fe: Fe is an important element for increasing the amount of intermetallic compounds and reducing the metallic luster after anodizing. Ie Fe
By increasing the amount and increasing the amount of the intermetallic compound in combination with the ingot homogenizing heat treatment condition, it is possible to suppress the metallic luster after the anodizing treatment and give a moist and calm texture. If the Fe content is less than 0.8%, the absolute number of intermetallic compounds is small, and the overall color becomes shallow and the color becomes silver, and the metallic luster becomes remarkable. On the other hand, the Fe content is 2.0%
If it exceeds, a coarse intermetallic compound will be produced. Therefore, the Fe content is set within the range of 0.8 to 2.0%.

Si: Si easily forms an abnormal structure called fir tree structure in the ingot. If a fir tree structure is generated in the ingot, a strip-shaped pattern called streak occurs on the surface when the rolled plate is anodized, and the appearance is impaired. In order to prevent the formation of this fir tree structure, it is necessary to control the Si content to 0.2 wt% or less.

Mn: Mn is an element that increases the redness of the color tone after anodizing treatment and is an essential element for obtaining a beige color tone. If the amount of Mn is less than 0.05%, the effect of giving a reddish color tone as a color tone after anodizing treatment is small, and a beige color cannot be obtained. On the other hand, when the amount of Mn exceeds 0.4%, the gray color becomes stronger and it deviates from the beige color. Therefore, the amount of Mn is 0.
It was set within the range of 05 to 0.4%.

In addition to the above Fe, Si, and Mn, Al and other inevitable impurities may be basically used.

In general aluminum alloys, a small amount of Ti, or Ti and B may be added for refining the crystal grains of the ingot, but in the case of the present invention, a small amount of Ti or
Ti and B may be added, and the effect of refining grain and streak of the rolled plate can be obtained by the crystal grain refining effect by the addition of these. In that case, if Ti is less than 0.003 wt%, the above effect cannot be obtained, while if Ti exceeds 0.15 wt%, a coarse intermetallic compound of TiAl ₃ may be produced, so that Ti is 0.003 to 0.15 wt%. It is preferably within the range. Further, B exhibits a grain refining effect when coexisting with Ti, but when B is less than 1 ppm, the effect cannot be obtained.
If it exceeds 0 ppm, linear defects due to coarse TiB ₂ particles will occur, so B is preferably in the range of 1 to 100 ppm.

Further, in the aluminum alloy plate of the present invention, in order to achieve a beige color tone with less metallic luster after anodizing treatment, the total amount of intermetallic compounds in the rolled plate state is 2.5 to 7.0.
It is within the range of wt% and the intermetallic compound amount (weight) is 90.
% Or more must be occupied by the FeAl ₃ phase and the FeMnAl ₃ phase. The reasons for limiting the conditions of these intermetallic compounds are as follows.

If the total amount of the intermetallic compounds is less than 2.5 wt%, the color tone after anodizing becomes shallow and the metallic luster becomes strong. On the other hand, if the total amount of the intermetallic compounds exceeds 7.0 wt%, the color tone after the anodic oxidation treatment becomes more gray and the beige color cannot be achieved. When the total amount of FeAl ₃ phase and FeMnAl ₃ phase in the total amount of intermetallic compounds is less than 90%, the color tone after anodizing treatment becomes grayish and the beige color tone cannot be achieved.

 Next, the manufacturing conditions will be described.

First, a molten aluminum alloy having the above-described compositional range is melted by a conventional method, and is cast by DC casting (semi-continuous casting). Here, the casting speed affects the generation of the fir tree structure in the ingot, and if the casting speed is too fast, the fir tree structure is likely to occur. If the casting speed is less than 35 mm / min, the productivity is too low to be economical, while at 150 mm / min
Above that, a fir tree structure occurs and streaks occur on the rolled plate, impairing the appearance. Therefore the casting speed is 35-150m
It is preferably within the range of m / min.

Then 0.5 to the ingot at a temperature in the range of 580 to 630 ° C.
Heat for ~ 24 hours. The heating of the ingot is not only necessary for general homogenization of the ingot structure but also has a great influence on the color tone after the anodizing treatment. That is, by heating this ingot, the intermetallic compounds FeAl ₆ and FeMnAl ₆ in the ingot become Fe
It transforms to Al ₃ or FeMnAl ₃ and Fe
The total amount of Al ₃ phase and FeMnAl ₃ phase accounts for 90% or more of the total amount of intermetallic compounds, and it becomes possible to obtain a beige color tone after anodizing the rolled plate. Ingot heating temperature
Below 580 ℃, FeAl ₃ phase and Fe in the plate of final thickness
The proportion of MnAl ₃ phase is less than 90%, the gray tone becomes strong after the anodizing treatment, and it cannot be called beige. On the other hand, when the ingot heating temperature exceeds 630 ° C., coarsening of crystal grains occurs, streaks occur after anodizing treatment, and local melting sometimes occurs. Therefore, the ingot heating temperature must be in the range of 580 ° C to 630 ° C. Further, if the ingot heating time is less than 0.5 hours, the above-mentioned effect is not sufficiently obtained, while if it exceeds 24 hours, the effect is saturated and only the cost is increased, so the time is limited to 0.5 to 24 hours.

After heating the ingot as described above, hot rolling and cold rolling are performed to obtain the final plate thickness. Here, hot rolling may be performed according to a conventional method, but it is generally performed at a heating temperature of the ingot or lower. Immediate annealing may be performed immediately after hot rolling or during cold rolling. The intermediate annealing is
It is common to carry out at 250 to 450 ° C for 0.5 to 12 hours.

In the rolled plate having the final plate pressure obtained as described above, the total amount of the intermetallic compounds is 2.5 to 7.0 wt as described above.
%, And the total amount of FeAl ₃ phase and FeMnAl ₃ phase must account for 90% or more of the total amount of intermetallic compounds. A beige color tone with less metallic luster can be obtained after the treatment.

Next, a process for actually obtaining a beige color tone by anodizing the rolled plate as described above will be described.

In the anodic oxidation treatment, degreasing and etching are generally performed in order to remove surface stains and surface defects in advance. The etching is usually a caustic soda-based alkali etching. The anodizing process itself uses a sulfuric acid bath with a H ₂ SO ₄ concentration of 10 to 250 vol%, a bath temperature of 10 to 30 ° C, and a current density of 1.5 A / dm ² or more and 2.5 A.
It is performed at less than / dm ² to form an anodized film having a thickness of 10 to 30 μm.

Here, when the H ₂ SO ₄ concentration of the sulfuric acid bath is less than 10 vol%, the porosity of the anodic oxide film formed is reduced and the bath voltage is increased. On the other hand, when the H ₂ SO ₄ concentration exceeds 25 vol%, the surface becomes rough and the anodic oxide film becomes soft. If the bath temperature is less than 10 ° C, it takes a long time to obtain the required film thickness, which is uneconomical. On the other hand, if the bath temperature exceeds 30 ° C, the corrosion resistance after anodizing is deteriorated. Furthermore, when the current density is 2.5 A / dm ² or more, a large amount of power is required for the treatment, which is not practical, while when the current density is less than 1.5 A / dm ² , the color tone after anodizing is light and a beige color is obtained. Disappear. Also, if the thickness of the anodized film formed is less than 10 μm, sufficient corrosion resistance cannot be obtained, while 30 μm
It is not economical to thicken it until it exceeds.

By the anodizing treatment with the sulfuric acid bath as described above, a beige color tone with less metallic luster can be obtained.
Here, the color tone after the anodizing treatment can be evaluated by the values of the lightness index L and the chromaticness indices a and b according to the Hunter color difference formula (see JIS Z8730). That is, the higher the L value of the lightness index is, the whiter it is, while the chromaticness index is about the coloring degree, the higher the a value is, the stronger the reddish color is, and the higher the b value is, the stronger the yellowish color is. The beige color tone that is the object of the present invention can be defined as a tone in which the L value, the a value, and the b value satisfy L> 65, 1 <a <4, and 2 <b <6. Further, the state in which the metallic luster is low can be defined as a gloss of 20% or less.

Example [Example 1] Molten alloy Nos. 1 to 6 shown in Table 1 were melted according to a conventional method, and a cross-sectional dimension of 400 mm was obtained by a semi-continuous casting method (DC casting method) at a casting speed of 65 mm / min. A 1000 mm ingot was cast. After chamfering each of the obtained ingots, the ingots were heated under the conditions shown in Table 2 (mainly 600 ° C × 10 hr, part of which was 530 ° C ×
After 10 hours), hot rolling was performed at 400 ° C. to obtain a hot rolled sheet having a thickness of 6 mm. Then, after cold rolling to a plate thickness of 4 mm, 350 ℃
Intermediate annealing was performed for 5 hours and cold rolling was performed to a plate thickness of 2.5 mm. However, for alloy No. 4, when the structure was confirmed at the ingot stage, a fir tree structure was generated, so no further rolling was performed.

Then, each plate was etched with a 5% NaOH aqueous solution, washed with water, and then desmutted with nitric acid. Then H ₂
Use a sulfuric acid bath with SO ₄ concentration of 15 vol%, bath temperature 20 ℃, current density
Anodizing at 2.0 A / dm ² and film thickness of 20 μm each
Of the anodic oxide film was generated.

The surface color tone of the anodized film of each plate was examined by using a color meter SM-3-MCH manufactured by Suga Test Instruments, and the surface glossiness was also examined. The color tone was evaluated using the lightness index L and the chromaticness index a and b according to Hunter's color difference formula. The results are shown in Table 2. When L value> 65, 1 <a value <4, 2 <b value <6 are satisfied and the glossiness is 20% or less, it can be determined that the color tone is beige with less metallic gloss.

On the other hand, for each plate, the total amount of intermetallic compounds and the ratio of the total amount of FeAl ₃ phase and FeMnAl ₃ phase to the total amount of intermetallic compounds were examined. The results are also shown in Table 2.

The amount of intermetallic compound was determined as follows. That is, first, about 0.5 to 1 g of a sample is taken and dissolved in 100 ml of a phenol solution at 170 to 180 ° C. for 30 minutes,
Further, 50 ml of benzyl alcohol was added at 140 ° C. to prevent coagulation of the phenol solution, the mixture was filtered, the residue was washed with alcohol, and the residue was subjected to gravimetric analysis.

The phase of the intermetallic compound was identified as follows. That is, first, about 0.5 to 1 g of a sample was taken, dissolved in 100 ml of a phenol solution at 170 to 180 ° C for 30 minutes, and benzyl alcohol was added to prevent coagulation of the phenol solution.
After addition of 50 ml at 0 ° C., filtration and washing of the residue with alcohol, the residue was identified by X-ray diffraction.

From the results shown in Table 2, it is clear that the aluminum alloy sheets according to the examples of the present invention can obtain a beige color having a moist texture with less metallic luster as a color tone after anodizing in a sulfuric acid bath. is there.

[Example 2] With respect to the rolled sheet of alloy No. 1 obtained in the same manner as in Example 1, the anodizing conditions were variously changed as shown in Table 3, and anodizing of a film thickness of 20 µm was performed. A film was formed.

Table 3 also shows the results of examining the color tone and gloss after anodizing treatment under each condition and the corrosion resistance of the anodized film. The corrosion resistance was evaluated by using the electromotive force method among the corrosion resistance test methods for anodic oxide coatings specified in JIS H8681, and 100 SEC or more was regarded as acceptable.

From the results shown in Table 3, an anodized film having a beige color tone which is excellent in corrosion resistance and has less metallic luster by anodizing in a sulfuric acid bath when the anodizing conditions specified in claim 3 are satisfied. It is clear that

EFFECTS OF THE INVENTION As is apparent from the above examples, the aluminum alloy sheet of the invention of claim 1 is moistened with less metallic luster, which has hitherto been difficult to achieve, by the economical anodic oxidation treatment with a sulfuric acid bath. A beige color tone with a texture can be obtained. According to the method of the invention of claim 2,
By appropriately controlling the conditions for heating the ingot, it is possible to practically manufacture the aluminum alloy plate exhibiting the color tone as described above after the anodizing treatment. Further, according to the method of the invention of claim 3, as the aluminum alloy plate subjected to the anodizing treatment, the anodizing plate having a beige color tone with less metallic luster and excellent corrosion resistance can be surely manufactured at low cost. Obtainable.

Claims (3)

(57) [Claims] 1. Fe 0.8-2.0 wt%, Mn 0.05-0.4 wt%, Si is regulated to 0.2 wt% or less, and the balance is substantially A.
FeA based on the total amount of intermetallic compounds (weight)
proportion of the total amount of l ₃ phase and FeMnAl ₃ phase is 90% or more, yet all intermetallics amount is equal to or within the range of 2.5～7.0Wt%, the color tone after the anodic oxidation treatment An aluminum alloy plate that is beige and has a low metallic luster. 2. Fe 0.8-2.0 wt% and Mn 0.05-0.4 wt% are contained, Si is regulated to 0.2 wt% or less, and the balance is substantially A.
made of aluminum alloy consisting of
After casting, at a temperature in the range of 580 ~ 630 ℃ for the ingot.
Heat treatment is applied for 5 to 24 hours, and then rolled to the final plate thickness, which gives FeAl to the total amount of intermetallic compounds (weight).
After anodizing, which is characterized by obtaining a rolled plate in which the total amount of the _three phases and FeMnAl ₃ phases occupies 90% or more and the total amount of intermetallic compounds is in the range of 2.5 to 7.0 wt%. A method for producing an aluminum alloy plate having a beige color tone and a low metallic luster. 3. Fe 0.8 to 2.0 wt% and Mn 0.05 to 0.4 wt% are contained, Si is regulated to 0.2 wt% or less, and the balance is substantially A.
made of aluminum alloy consisting of
After casting, at a temperature in the range of 580 ~ 630 ℃ for the ingot.
Heat treatment is applied for 5 to 24 hours, and then rolled to the final plate thickness, which gives FeAl to the total amount of intermetallic compounds (weight).
_A rolled plate having a total amount of ₃ phases and FeMnAl ₃ phases of 90% or more and a total intermetallic compound content within the range of 2.5 to 7.0 wt% is obtained, and then H ₂ SO is added to the rolled plate. ₄ Using a sulfuric acid electrolytic bath with a concentration of 10 to 25 vol%, bath temperature 10 to 30 ° C,
A beige color tone after anodizing, characterized by forming an anodizing film with a film thickness of 10 to 30 μm by anodizing at a current density of 1.5 A / dm ² or more and less than 2.5 A / dm ^2. And a method for producing an aluminum alloy plate having a low metallic luster.